Effects Of Heavy Metal Pollution Research Articles

Assessment of Effects of Amended Bioremediation of Toxic Metal-polluted Soil using Organic Composites and Bacillus sp on Plant Growth Parameters

It has become pertinent to develop improved bioremediation techniques, to avert the deleterious effects of heavy metal pollution on agricultural productivity, and safety of its produce. In this study, cow dung, poultry wastes and their composites used as organic amendments were collected and processed, while Bacillus sp used as plant growth promoting rhizosphere was isolated and identified. Then 24 kg of fertile soil was polluted by introducing 20 mL of 0.1M lead acetate solution, before bagging 5 kg of polluted soil into ten perforated nylons. Soil sample was then analyzed before and after treatment. After mixing with Bacillus sp suspension, two of the pot experiments were amended with each of 0.5 kg cow dung only, 0.5 kg poultry wastes only and 1:1 ratio of their composites. Control samples were set up without amendment, and they were bioremediated for 25 days. Following germination of sown corn seedlings, heights of their shoots and number of leaves were monitored on day 4, weeks 2, 4 and 7, before harvesting for analysis together with soil samples. Results obtained revealed that seedlings grown on treated samples as well as properties of treatment of soil were generally better than those of control samples. Highest percentage increase in organic matter content of soil was recorded in treatment with mixture of cow dung only and Bacillus sp, with 9.28% and 7.63% increase at 33.75 mg/kg and 52.55 mg/kg of lead (Pb) pollution. Seedlings grown on samples treated with poultry wastes only, recorded the highest protein content of 161.25±5.5 mg/g, 104.99±4.95 mg/g and 79.75±3.2 mg/g protein contents, at 32.75 mg/kg, 42.02 mg/kg and 52.44 mg/kg levels of Pb pollution, respectively. The amendments also reduced bioaccumulation of Pb in corn seedlings, which was in the order; stem<leaf<root. Therefore, these amendments can be exploited for improved bioremediation of heavy metals.

Potential of Plant Based Metallophytes for Phytoremediation in Agriculture

Metallophytes are the unique group of plants that have evolved to thrive in metal rich environments and have drawn plenty of attention. Remediating heavy metal contaminated places with plants is an effective choice due to phytoremediation, an environmentally friendly method that uses plants to mitigate the pollution. Metallophytes are ideal options for phytoremediation applications due to their inherent traits such as hyper-accumulation, efficient metal absorption and tolerance mechanisms impacting both the plant and soil. These plants absorb and translocate heavy metals, detoxifying the soil while accumulating them in tissues. This reduces metal toxicity in soil and holds potential for resources recovery. The role of metallophytes in phytoremediation is analysed in this review with particular focus given to their ways of metal absorption, translocation and detoxification. Metallophytes have high metal tolerance and accumulation capacities due to their unique physiological and biochemical adaptations including enhanced metal sequestration in vacuoles, metal chelation by phytochelatins and activation of anti-oxidant defence systems. This review also highlights the significance of metallophytes in enhancing the soil health, reducing metal bioavailability, and promoting the ecological sustainability as well as their potential for restoring contaminated ecosystems. Utilizing the unique capabilities of metallophytes obtained from plants possesses enormous possibilities to minimise the negative effects of heavy metal pollution, protect ecosystems, and promote sustainable development for future generations. Eventually, it outlines future research approaches that aim to enhance metallophytes based phytoremediation strategies, widen their implementation and include them in holistic approaches for environmental restoration and sustainable land management.

Understanding the detrimental effects of heavy metal pollution in shrimp farming and treatment methods – a review

Abstract High levels of heavy metals in the environment pose a significant risk to the aquatic ecosystem and its organisms. The non-biodegradable nature and lengthy persistence of heavy metals in the environment lead to toxicity in shrimp. Using aquatic animals as bio-indicators of metal contamination provides valuable data on acute and chronic toxicity in aquatic species and environmental quality. This review aims to provide insights into the sources, impacts, diseases and mitigation strategies related to heavy metal pollution in shrimp farming and the dangers to humans. Shrimp growth and development at each stage exhibit distinct responses to toxicity, which can vary depending on the species, types of metals, their mechanisms of action, as well as the concentration of heavy metals and duration of exposure. While several heavy metals are considered essential nutrient elements that enhance shrimp growth and feed efficiency, exceeding the maximum tolerable limit threatens shrimp health, human consumers, and ecological systems’ stability. Shrimp species subjected to lethal toxic metal concentrations experience significant effects on accumulation in histopathology. Heavy metal toxicity has been linked to high mortality rates, malformation rates, oxidative stress, moulting issues, and decreased reproduction with increasing concentrations in shrimp. Various methods have been reported for removing heavy metal ions from aquatic environments, including filtration, adsorbents, removal efficacy, operating conditions, and the pros and cons of each technique. Therefore, this review provides an overview of how heavy metals can affect shrimp physiology and dangers to consumers. It aims to increase awareness about the importance of preventing and regulating their contamination in aquatic environments.

Effects of Cadmium Stress on Seed Germination and Physiology and Biochemistry during Early Seedling Growth of Masson Pine (Pinus massoniana Lamb.)

Abstract This study evaluated the effects of cadmium (Cd) on seed germination and the physiological and biochemical characteristics of Pinus massoniana, which was used as the experimental material; culture dishes and germination boxes were used as testing devices. Seed germination and seedling growth in the presence of various Cd concentrations (0.4, 0.8, 1.2, 2, and 0 mg/L) were explored. The germination indexes of Pinus massoniana seeds used were germination percentage (GP), germination energy (GE), germination index (GI), vigor index (VI). and embryo length. The indexes of early growth of seedlings used were soluble sugar and soluble protein content, antioxidant enzyme activity, Cd content, and Cd enrichment. We found that Pinus massoniana presented reduced GP, GE, GI, VI, and embryo length with increasing Cd concentrations, and the VI and embryo length significantly decreased (P < .05). The physiological and biochemical indexes of Pinus massoniana seedlings were promoted at low Cd concentrations and inhibited at high Cd concentrations; each index peaked under 0.4 mg/L Cd. The Cd content in seedlings and the degree of enrichment decreased and then increased with increasing Cd concentration. Grey correlation analysis results showed that the effects of Cd stress were the strongest on embryo length in seeds (correlation degree: 0.769). Study Implications The effect of heavy metal pollution on seed germination and growth is closely related to phytoremediation of heavy metal soil. Pinus massoniana is the most widely distributed pine species in China. It is an economically important industrial timber with important ecological value. This study found that under the stress of different cadmium concentrations, heavy metal Cd stress inhibited the germination of Pinus massoniana seeds, and moderate Cd concentration promoted the physiological and biochemical of Pinus massoniana seedlings. Pinus massoniana seedlings have the ability to enrich heavy metal Cd.

How plants respond to heavy metal contamination: a narrative review of proteomic studies and phytoremediation applications.

Heavy metal pollution caused by human activities is a serious threat to the environment and human health. Plants have evolved sophisticated defence systems to deal with heavy metal stress, with proteins and enzymes serving as critical intercepting agents for heavy metal toxicity reduction. Proteomics continues to be effective in identifying markers associated with stress response and metabolic processes. This review explores the complex interactions between heavy metal pollution and plant physiology, with an emphasis on proteomic and biotechnological perspectives. Over the last century, accelerated industrialization, agriculture activities, energy production, and urbanization have established a constant need for natural resources, resulting in environmental degradation. The widespread buildup of heavy metals in ecosystems as a result of human activity is especially concerning. Although some heavy metals are required by organisms in trace amounts, high concentrations pose serious risks to the ecosystem and human health. As immobile organisms, plants are directly exposed to heavy metal contamination, prompting the development of robust defence mechanisms. Proteomics has been used to understand how plants react to heavy metal stress. The development of proteomic techniques offers promising opportunities to improve plant tolerance to toxicity from heavy metals. Additionally, there is substantial scope for phytoremediation, a sustainable method that uses plants to extract, sequester, or eliminate contaminants in the context of changes in protein expression and total protein behaviour. Changes in proteins and enzymatic activities have been highlighted to illuminate the complex effects of heavy metal pollution on plant metabolism, and how proteomic research has revealed the plant's ability to mitigate heavy metal toxicity by intercepting vital nutrients, organic substances, and/or microorganisms.

The Effects of Heavy Metal Pollution on Soil Nitrogen Transformation and Rice Volatile Organic Compounds under Different Water Management Practices.

One of the most concerning global environmental issues is the pollution of agricultural soils by heavy metals (HMs), especially cadmium, which not only affects human health through Cd-containing foods but also impacts the quality of rice. The soil's nitrification and denitrification processes, coupled with the release of volatile organic compounds by plants, raise substantial concerns. In this review, we summarize the recent literature related to the deleterious effects of Cd on both soil processes related to the N cycle and rice quality, particularly aroma, in different water management practices. Under both continuous flooding (CF) and alternate wetting and drying (AWD) conditions, cadmium has been observed to reduce both the nitrification and denitrification processes. The adverse effects are more pronounced in alternate wetting and drying (AWD) as compared to continuous flooding (CF). Similarly, the alteration in rice aroma is more significant in AWD than in CF. The precise modulation of volatile organic compounds (VOCs) by Cd remains unclear based on the available literature. Nevertheless, HM accumulation is higher in AWD conditions compared to CF, leading to a detrimental impact on volatile organic compounds (VOCs). The literature concludes that AWD practices should be avoided in Cd-contaminated fields to decrease accumulation and maintain the quality of the rice. In the future, rhizospheric engineering and plant biotechnology can be used to decrease the transport of HMs from the soil to the plant's edible parts.

Effects of heavy metal contamination on fungal diversity in Pinus brutia shoots

The effects of heavy metal pollution have become a significant global issue in recent years. The primary objective of the present study was to compare the heavy metal concentrations in Pinus brutia shoots grown in an organized industrial zone (OIZ) and a forested area (Adalar) and to examine how these heavy metals affect fungal microbiota. The results achieved here showed that Ni and V concentrations were lower than the detectable limits in both the Adalar and the OIZ region, whereas Se and Cu concentrations were lower than the detectable limits in the shoots collected from the Adalar. Concentrations determined in samples collected from the OIZ were approximately 6 times higher for Cr and 16 times higher for Zn in comparison to the samples collected from the Adalar. Metagenomic analysis revealed that the most common fungal genera were Aureobasidium, Gibberella, Hazslinszkyomyces, Alternaria, Cladosporium, Buckleyzyma, Lasiodiplodia, and Hormonema for the OIZ area and Hormonema, Aureobasidium, Alternaria, Cladosporium, Arthrinium, Fonsecazyma, and Truncatella for the Adalar region. In the future, this study may serve as a reference for the development of innovative strategies for the remediation of heavy metal pollution for a sustainable and clean environment using biological sources.

Exposure to polymetallic contaminated sites induced toxicological effects on chicken lungs: A multi-level analysis

Heavy metal pollution is an important environmental issue causing several hazards to organisms. In the present study, we investigated the uptake and accumulation of heavy metals (Pb, Cd, Cu, and Zn) in chicken lungs after six months of breeding on polymetallic-contaminated area in Jebel Ressas village. Genotoxicity in term of micronuclei frequency as well as oxidative stress in term of enzymatic activities of Catalase (CAT), Glutathion-S-Transferase (GST) and malondialdehydes accumulation (MDA) were performed. In addition, gene expression levels involved in oxidative stress genes (cat, sod and gst), metal homeostasis (mt1 and mt4) and DNA metabolism (p53, bcl2, caspase 3 and DNA ligase) were detected. Exposed chicken lungs revealed an important heavy metal accumulation of Cd and Zn co-occurring with oxidative status modulation. Transcriptomic results unveiled an upregulation of oxidative stress and homeostasis genes. On the other hand, genes involved in DNA metabolism indicated cellular functioning towards cells death and apoptosis modulation. Moreover, the histopathological examination revealed lung lesions in the chickens exposed to heavy metal contamination. Our study highlights the hazardous effects of heavy metal pollution on chicken respiratory system.

Inversion of heavy metal content in soil using hyperspectral characteristic bands-based machine learning method

The global concern regarding the adverse effects of heavy metal pollution in soil has grown significantly. Accurate prediction of heavy metal content in soil is crucial for environmental protection. This study proposes an inversion analysis method for heavy metals (As, Cd, Cr, Cu, Ni, Pb) in soil based on hyperspectral and machine learning algorithms for 21 soil reference materials from multiple provinces in China. On this basis, an integrated learning model called Stacked RF (the base model is XGBoost, LightGBM, CatBoost, and the meta-model is RF) was established to perform soil heavy metal inversion. Specifically, three popular algorithms were initially employed to preprocess the spectral data, then Random Forest (RF) was used to select the best feature bands to reduce the impact of noise, finally Stacking and four basic machine learning algorithms were used to establish comparisons and analysis of inversion model. Compared with traditional machine learning methods, the stacking model showcases enhanced stability and superior accuracy. Research results indicate that machine learning algorithms, especially ensemble learning models, have better inversion effects on heavy metals in soil. Overall, the MF-RF-Stacking model performed best in the inversion of the six heavy metals. The research results will provide a new perspective on the ensemble learning model method for soil heavy metal content inversion using data of hyperspectral characteristic bands collected from soil reference materials.

Effects of heavy metal pollution on population dynamics of another important pollinator insect group: Horseflies (Diptera: Tabanidae)

Horseflies represent important agents of pollination as well as other pollinator insects, like butterflies, bees and wasps. Horseflies belong to the genera Atylotus, Dasyramphis, Glaucops, Pangonius, Philoliche, Chrysops, Hybomitra, and Tabanus species are exclusive nectar feeders. Glucose, fructose and sucrose are major components of plant nectars which are used nourishing for developing eggs. Because of these features horseflies have a significant role in pollination of phanerogams. This study was conducted to investigate the effects of toxic heavy metals on the population dynamics of horsefly species. Monthly changes on the accumulation of heavy metals in the larval habitats of horsefly species were determined with Perkin Elmer Optical Spectrophotometer and also correlations between concentrations of heavy metals and population fluctuations of horse fly species were observed. The results demonstrated that lead, iron and cadmium have statistically important negative effects on the population dynamics of horsefly species.

Analysis of antioxidants in water striders (Hemiptera: Gerridae) as bioindicator of water pollution.

The antioxidant enzyme system is an important defense mechanism to cope with Reactive Oxygen Species (ROS) produced due to exposure to heavy metals. In the present study lead (Pb), chromium (Cr), arsenic (As), cadmium (Cd) and nickel (Ni) in water and the antioxidant activity of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) was investigated in three species (Metrocoris communis, Limnogonus fossarum fossarum, and Aquarius adelaidis) of water striders collected from the industrial triangle of Punjab, Pakistan. The results of present study revealed that Pb, Cr, As, Cd and Ni were according to the permissible amount of WHO. The antioxidant activity of SOD, CAT and POD was found significantly different among species against oxidative stress, but found the highest activity of determining parameters in A. adelaidis. This is one of the pioneer studies in Pakistan reporting the role of water striders as a bioindicator of heavy metals present in the water through antioxidants enzyme variations. The current results supported that variant level of antioxidant enzyme activities in different species of water strider were reflective of heavy metal pollution in the Industrial triangle of Punjab, Pakistan and will be a useful ecotoxicological tools to evaluate the detrimental effects of heavy metal pollutants in aquatic organisms.

Mechanisms of microbial-driven changes in soil ecological stoichiometry around gold mines

In this study, we used soils with different pollution and nutrient levels (non-polluted S1, highly polluted low-nutrient S2, and highly polluted high nutrient S3) around the gold mine tailing ponds, and combined with metabolic limitation modeling and macro-genomics approaches, aiming to investigate the relationship between soil microbial composition and soil eco-chemometrics characteristics under heavy metal stress. The results showed that heavy pollution resulted in reduced SOC, TN, microbial biomass, and with C- and P- acquisition (BG, CBH, ALP) as well as nitrogen limitation of soil microbial metabolism in soils (S2, S3). Further analysis by macrogenomics showed that heavy metal contamination led to an increase in α-microbial diversity and altered the composition of microbial communities in the soil. The cycling of C, N, and P nutrients was altered by affecting the relative abundance of Anaeromyxobacter, Steroidobacter, Bradyrhizobium, Acidobacterium, Limnochorda (predominantly in the Ascomycetes and Acidobacteria phyla), with the most pronounced effect on the composition of microorganisms synthesizing C-acquiring enzymes, and heavy metals and pH were the main influences on ecological stoichiometry. The results of this study are useful for understanding the sustainability of ecological remediation in heavy metal contaminated areas and for developing ecological restoration strategies.

Substantial and efficient adsorption of heavy metal ions based on protein and polyvinyl alcohol nanofibers by electrospinning

The adverse effects of heavy metal pollutants in wastewater have threatened human health in recent decades. Therefore, the development of absorbents for such pollutants is essential to overcome these problems. Electrospun nanofibers are often used for wastewater treatment owing to their high porosity and high specific surface area. Zein from plants and collagen from animals are vulnerable to moisture, which limits its broad application in practice. However fully biodegradable polyvinyl alcohol (PVA), which is soluble in water, can be mixed with protein individually to overcome the limitation. In this work, the two proteins described above and PVA were combined to prepare protein nanofibers by electrospinning technology, which could achieve adsorption of Cu2+. As the protein content increased, the adsorption properties of the obtained nanofibers for Cu2+ showed a rising and then decreasing trend, with the highest point at 50 % of protein content, especially the collagen nanofibers, which reached 24.62 mg/g. Both protein nanofibers reached adsorption equilibrium after 15 h, but overall, collagen nanofibers showed a superior adsorption performance for Cu2+ than that by zein nanofibers. In the process of Cu2+ adsorption by protein nanofibers, both physical and chemical effect existed, and the physical effect played the leading role.

Long non-coding RNAs regulate heavy metal-induced apoptosis in embryo-derived cells

Heavy metal pollution has been a worldwide prevalent problem, and particularly a threat to ecosystem integrity and animals’ health. Previous studies on the mechanisms of heavy metal toxicity have focused on protein-coding genes, whereas most genomic transcripts are long non-coding RNAs (lncRNAs). Although lncRNAs are known to play important regulatory roles in biological processes, their role in heavy metal stress regulation is still not fully understood. We here developed an insect embryo cell model for studying metal toxicity and the underlying regulatory mechanisms. We performed genome-wide screening and functional characterization of lncRNAs induced by two essential and two non-essential heavy metals in Drosophila embryo-derived S2 cells. We identified 4894 lncRNAs, of which 1410 were novel. Forty-one lncRNAs, together with 328 mRNAs, were induced by all the four heavy metals. LncRNA–mRNA co-expression network and pathway enrichment analysis showed that detoxification metabolism, circadian rhythm, and apoptosis regulation pathways were activated in response to heavy metal stress. LncRNA CR44138 was remarkably upregulated in cells exposed to the four heavy metals and was associated with the apoptosis pathway. Expression interference confirmed that CR44138 aggravated cytotoxicity-induced apoptosis in cells under heavy metals stress. This study highlights the important role of lncRNAs in regulating the cellular response to heavy metals. This study also lays the foundation for discovering the novel regulatory mechanisms and developing diagnostic biomarkers of the toxic effects of heavy metal pollutants on organisms.

Assessment of heavy metal pollution of drinking water sources and staple food cultivars around artisanal mining site in Igade-Mashegu, Niger State, Nigeria

Ecotoxicological studies have been carried out on the precarious effects of heavy metal pollution and exposure attributed to anthropogenic practices such as mining, industrial and agricultural activities, which poses serious health challenges. This study investigated ten (10) heavy metals namely As, Cd, Co, Cr, Cu, Fe, Hg, Ni, Pb and Zn in one hundred and fifteen samples from water sources and staple food cultivars around Igade mining site in Mashegu Local Government Area of Niger State, North-Central Nigeria, using Atomic Absorption Spectrophotometer (AAS). The result revealed the concentrations of heavy metals in staple food cultivars consumed at Igade to be within the recommended maximum levels as stipulated by WHO/FAO, but As2+ and Cd2+ were higher in legumes (1.510 ± 0.169 mg/kg) and vegetables (1.666 ± 0.154 mg/kg); and cereals (0.328 ± 0.012 mg/kg) and tubers (0.421 ± 0.176 mg/kg) respectively. This implies that the artisanal mining contributed to the exogenous bioaccumulation of these metals in staple food cultivars following the pattern: Fe > Zn > Cu > As > Pb > Cr > Cd > Hg which could accumulate and destroy vital organs thereby affecting human health upon consumption. Also, the mean concentration of the heavy metals in various water sources at Igade mining site decreased in the order Zn > Fe > Cr > Cu > As > Hg > Pb > Cd > Ni. Levels of As, Hg, Pb, Fe, and partly Cr in water sources were observed to be higher than the WHO and NSDWQ recommended standards for drinking water. Thus, their continuous consumption poses potential health risk to inhabitants, and therefore, there is need for the provision of safe alternative water sources; proper sensitization and monitoring of the mining activities to curb health risks and the extent of heavy metal contamination.

The use of muscle biomarkers for assessing physiological effects of heavy metal pollution in the greater white-toothed shrew (Crocidura russula)

The greater white-toothed shrew Crocidura russula has been used as a sentinel species for estimating environmental risks to human populations. Previous studies in mining areas have focused on the liver of shrews as the primary target of physiological and metabolic changes due to heavy metal pollution. However, populations persist even when detoxification by the liver seems to be compromised and damage is observed. These pollutant-adapted individuals inhabiting contaminated sites may exhibit altered biochemical parameters that confer increased tolerance in various tissues other than the liver. The skeletal muscle tissue of C. russula might be an alternative tissue that allows the survival of organisms inhabiting historically polluted sites due to the detoxification of redistributed metals. Organisms from two heavy metal mine populations and one population derived from an unpolluted site were used to determine the detoxification activities, antioxidant capacity, and oxidative damage, as well as cellular energy allocation parameters and acetylcholinesterase activity (a biomarker of neurotoxicity). Muscle biomarkers differ between shrews from polluted sites and shrews from the unpolluted location, with the mine animals showing: (1) a decreased energy consumption concomitant with increased energy reserves and total available energy; (2) reduced cholinergic activity, suggesting an impairment of neurotransmission at the neuromuscular junction; (3) an overall decrease in detoxification capacity and enzymatic antioxidant response and a higher level of lipid damage. Also, some of these markers differed between females and males. These changes may have resulted from a decreased detoxifying capacity of the liver and could potentially bring about significant ecological effects for this highly active species. Heavy metal pollution induced physiological changes in Crocidura russula showing that skeletal muscle may serve as a backup sink organ allowing rapid species adaptation and evolution.

Toxic effects of heavy metals pollution in the selected stretches of Ganga river on aquatic flora, fauna and human health

Toxic effects of heavy metals pollution in the selected stretches of Ganga river on aquatic flora, fauna and human health

Effects of Heavy Metal Pollution on the Structure of Microbial Communities in Different Habitats

Heavy metal pollution seriously threatens the diversity and composition of microbial communities in various ecosystems. However, little is known about the effects of heavy metal pollution on the structure of microbial communities in the three habitats of "surface water-sediment-groundwater." Here, with help of 16S rRNA high-throughput sequencing technology, the diversity and composition of microbial communities, as well as the underlying controlling factors, were investigated and compared among the surface water, sediment, and groundwater of the Tanghe sewage reservoir. The results showed significant differences in the diversity of microbial communities among different habitats, with the highest α diversity observed in groundwater rather than surface water or sediment. Meanwhile, microbial communities also displayed distinct compositions among the three different habitats. Specifically, Pedobacter, Hydrogenophaga, Flavobacterium, and Algoriphagus were dominant in surface water; metal-tolerant bacteria such as Ornatilinea, Longilinea, Thermomarinilinea, and Bellilinea prevailedin sediment; and Arthrobacter, Gallionella, and Thiothrix were abundant in groundwater. Furthermore, physicochemical factors and metal variables jointly determined the microbial community structure in the three habitats. Among the influencing factors,pH, NO3--N, and Li were the main factors affecting the microbial structure in surface water; TP, NH4+-N, Cr, Fe, Cu, and Zn significantly impacted microorganisms in sediment; and only pH (not metal pollutants) was weakly associated with the microbial composition in groundwater. Overall, heavy metal pollution significantly shaped the microbial community structure in sediment, followed by that in surface water and groundwater. These results provide important scientific guidance for the ecological restoration and the sustainable development of heavy metal-polluted ecosystems.

Effects of heavy metal pollution and soil physicochemical properties on the Sphagnum farmland soil microbial community structure in Southern Guizhou, China

Farmland soil pollution is a serious problem worldwide threatening environment and human health. Microbial communities plays a key role in soil function. The purpose of this study was to analyze the relationship between microbial structure and soil physicochemical properties under different heavy metal pollution levels, find out heavy metal tolerant species under different environmental conditions, then provide useful reference for the bioremediation of contaminated farmland. In this study, 16s rRNA high-throughput sequencing technology was used, multiple comparisons and correlation analyses of the data were performed using R software. The results showed that study area A was contaminated by heavy metal Cd, and study area A, B and C were contaminated by heavy metal Hg. From the analysis of the community structure of the samples, it can be seen that the dominant bacterial phyla were Proteobacteria, Acidobacteriota, Chloroflexi, Actinobacteria, and 10 others. Correlation and RDA analysis of samples showed that the heavy metals Hg and As in peat were related to dominant bacteria phyla, and the physicochemical properties of soil potential of hydrogen (pH), total nitrogen (TN), available nitrogen (AN), available phosphorus (AP), available potassium (AK), and soil organic matter (SOM) were significantly positively correlated with the bacteria (Acidobacterta and Chloroflexi). Moreover, Chloroflexi was more tolerant to the heavy metals Hg and As. There was a significant correlation between bacterial community abundance and diversity in the four study areas. Soil heavy metal concentration and soil physicochemical properties affected the main phyla, bacterial community abundance and bacterial diversity of peat soil. These results indicate that some microorganisms have strong tolerance to heavy metal pollution and certain heavy metal digestion ability, which can create a good environment for farmland soil remediation.

Effects of Heavy Metal Pollution in Soil of Coal Gangue Area on Germination and Seedlings of Typical Remediation Plants

The problem of soil heavy metal pollution caused by coal gangue accumulation areas is becoming more and more serious. In situ plant remediation technology has become one of the most promising methods to solve heavy metal soil pollution due to its advantages of the green economy. In this experiment, the characteristics of heavy metal pollution in the shallow soil (vertical depth 0~20 cm) 300 m outside the square circle of a typical coal gangue accumulation area in the Fengfeng Mining Area of Hebei Province, China were used as the prototype. Alfalfa and ryegrass were selected as the test plants. Pot experiments were carried out at different heavy metal concentrations (Cu:14/64/100 mg/kg, Pb:15/38/170 mg/kg, Cd:1/4/8 mg/kg) levels to study and reveal the effects of single and compound soil heavy metal pollution on seed germination and seedling growth characteristics of alfalfa and ryegrass. The results showed that: (1) Under the condition of single Cd pollution, the germination index of alfalfa seeds and the germination potential of ryegrass seeds show a trend of “low concentration promotion and high concentration inhibition”. Under the condition of single Pb and Cu pollution in soil, the germination indices show obvious inhibition and damage effect; that is, with an increase in concentration, the germination rate, germination potential, germination potential, and vigor index show a decreasing trend. When Pb is 170 mg/kg or Cu is 100 mg/kg or Cd is 8 mg/kg, the inhibitory effect on seed germination and seedling growth of the two plants is the most harmful. (2) Due to the different concentrations of heavy metal combined pollution, there are synergistic or antagonistic effects between Cu, Pb and Cd in soil on alfalfa and ryegrass. That is to say, under low concentrations of heavy metal pollution, the inhibitory effect of combined stress is greater than that of single stress, and under high concentration of heavy metal pollution, the inhibitory effect of combined stress is less than that of single stress. (3) Whether in the single pollution or combined pollution of soil, ryegrass is always more tolerant than alfalfa, indicating that ryegrass has more potential for remediation.